It has conventionally been well known to use a siliceous film as an insulating film, a dielectric film, a protective film or a hydrophilicity-imparting film. As a method for forming such siliceous film on a base material, there have been employed various methods such as a PVD method (sputtering method or the like), a CVD method, a sol-gel method and a method of forming a polysiloxane or polysilazane coat and converting this coat to a siliceous film by calcination or the like. Of these methods, the PVD method and the CVD method involve the problem that they require expensive apparatuses and complicated control for forming a good coat. Also, the sol-gel method involves a problem that it requires a calcination temperature as high as 500° C. or higher. Further, the method of using polysiloxane involves a problem that cracks are generated due to reduction in thickness of formed film. On the other hand, the method of applying a polysilazane solution to form a coat and converting this coat to a siliceous film has been particularly noted in recent years since it enables one to easily form a siliceous film having excellent properties by low-temperature calcination and the formed siliceous film has excellent film quality.
The siliceous film is being widely utilized as, for example, an interlayer dielectric film, a planarization film, a passivation film or an element-separating insulator for semiconductor elements in LSI or TFT liquid crystal devices. In the case of forming such siliceous film in semiconductor elements or the like, the following method is commonly employed. That is, first, a polysilazane solution is spin-coated on a substrate having a stepped or non-stepped surface and, as needed, having formed thereon semiconductors, wiring or electrodes, and is heated to remove a solvent from the coat, followed by calcination at a temperature of 350° C. or above to convert polysilazane to a siliceous film. The thus-converted siliceous film is utilized as an interlayer dielectric film, a planarization film, a passivation film or an element-separating insulator. In these methods, however, it is well known that, upon spin-coating the polysilazane solution on a substrate, beads are formed at the periphery of the substrate and, at the same time, the solution spreads to the back side of the substrate. In order to prevent non-uniformity in thickness of the coat at the periphery of the substrate generated by the beads, it is usually conducted to rinse the edge in forming the polysilazane film by applying the polysilazane solution and, at the same time, back rinse in order to remove polysilazane having spread and deposited onto the back side of the substrate to thereby clean the back side.
In some cases, it is required to peel off the coated polysilazane film formed according to the above-mentioned method from the substrate, and it is also required to wash away polysilazane having deposited on a coating apparatus such as a spin-coater. It has conventionally been known to use, for example, propylene glycol monomethyl ether acetate (PGMEA) as a rinsing solution or a peeling solution for removing polysilazane. However, the known rinsing solution or peeling solution involves such problem as that polysilazane cannot be fully rinsed away or peeled off or that, though polysilazane is fully rinsed away or peeled off, there sometimes arises clogging of a waste liquor line for a coating apparatus such as a spin-coater due to gelation of the waste liquor or generation of a gas such as silane, hydrogen or ammonia in a waste liquor tank. In the case where gelation of the waste liquor takes place, it is required to often wash the coating apparatus and the waste liquor line and, in the case where a silane gas or the like generates in the waste liquor tank and the concentration of silane exceeds the spontaneous ignition limit, there arises an extremely dangerous state that explosion takes place the moment that the lid of the waste liquor tank is opened.
The siliceous film formed from the polysilazane coat is being used in various fields as a dielectric film, an insulating film or a partitioning film for a liquid crystal display device or a plasma display panel (PDP) and, further, as a protective film for various articles such as the surface of car body, interior or exterior furnishings of a house, glass products, china and porcelain products and plastic products other than the field of semiconductor elements. Also in these fields, there sometimes arises the problem that the polysilazane film having deposited onto unnecessary portions to be coated must be removed as is the same with the case of producing semiconductor elements.
An object of the present invention is to provide a solvent for treating polysilazane, which does not cause the above-mentioned problems upon rinsing or peeling of a polysilazane coat or a coated film, and a method of treating polysilazane by use of the solvent.
That is, the object of the present invention is to provide a solvent for treating polysilazane, which shows excellent properties of dissolving polysilazane and does not adversely affect the properties of a ground such as a semiconductor or a substrate and properties of the remaining polysilazane coat, and a method of treating polysilazane by use of the solvent.
Another object of the present invention is to provide a solvent for treating polysilazane, which shows, in addition to the above-mentioned properties, excellent edge-cutting properties for a polysilazane coat and scarcely decomposes polysilazane, and a method of treating polysilazane by use of the solvent.